Static neutralization systems are well known in the art and are commonly utilized at various stages of product fabrication and packaging to remove potentially interfering, electrostatic charges from materials that readily develop static electricity, such as paper and plastic. Conventionally, static neutralization systems operate by emitting a field of positive and negative ions that neutralize any electrostatic charge present on the treated material.
Static neutralization systems typically comprise one or more high-voltage, air-ionizing, anti-static electrodes, or bars, which are electrically coupled to a common, alternating current (AC) power supply capable of producing relatively high voltages (e.g., in the order of 7.5 kV). Once electrically coupled to the power supply, each elongated, linear, anti-static bar is manually manipulated or fixedly mounted to best serve the intended static removal application. An example of an anti-static bar, or static eliminator, is disclosed in U.S. Pat. No. 3,120,626 to H. Schweriner, the disclosure of which is incorporated herein by reference.
Referring now to FIG. 1, there is shown a simplified schematic representation of a conventional, high-voltage, AC power supply 11 for use in static neutralization systems. As can be seen, power supply 11 includes a generally enclosed, box-shaped, outer housing, or chassis, 13 into which is disposed a supply circuit 15. Supply circuit 15 typically comprises a high-voltage transformer 17 for stepping up, or increasing, the voltage produced from an external AC power source 19 (e.g., AC mains electricity). Transformer 17 generally includes a laminated core 21 that is connected to external AC power source 19 by a primary winding 23. A pair of high-voltage, output connectors 25-1 and 25-2, each of which terminates into an externally accessible, output port 27 (e.g., an electrical socket with spring coupling means for quick connection/disconnection), is connected to a secondary winding 29 for transformer 17 via a common contact 31, such as a screw contact. Additionally, transformer 17 commonly includes a magnetic shunt 33 between primary winding 23 and secondary winding 29 in order to limit the output current and to control imbalances in flux between windings 23 and 29.
During the assembly process, at least a portion of core 21, output connectors 25, secondary winding 29 and contact 31 are encapsulated within a generally cup-shaped, dielectric block 35, as shown in simplified form in FIG. 1. Dielectric block 35 serves, inter alia, to limit the effects of any partial discharge of electricity along the voltage supply path. Furthermore, a dielectric potting compound, such as asphalt, is often deposited into certain voids within chassis 13 to suppress any noise and/or minimize the risk of a shunt condition in response to an electrical discharge along the voltage supply path.
Although well known in the art and widely used in commerce, conventional high-voltage, AC power supplies of the type described in detail above have been found to suffer from a few notable shortcomings.
As a first shortcoming, conventional high-voltage, AC power supplies of the type described in detail above have been found to be unreliable and prone to early operational failure. In particular, conventional high-voltage, AC power supplies have been found to exhibit partial discharge (i.e., a discharge of electricity that results in a breakdown of dielectric material within a region of contact between conducting elements) below operating voltage. If any dielectric material either (i) inadequately encapsulates electrical components along the supply path (e.g., due to imperfections in the block that create small air cavities) or (ii) breaks down, or becomes otherwise damaged, a discharge of electricity can result in a shunt condition, which may render the power supply inoperable or otherwise damaged.
Traditional high-voltage, AC power supplies often utilize a variety of different techniques to remedy the effects of partial discharge. One technique for minimizing the effects of partial discharge involves utilizing a dielectric material that is less susceptible to breakdown, such as an oil-based or gas-based dielectric. Another technique for minimizing the effects of partial discharge involves vacuum encapsulating regions prone to discharge (e.g., at the point of connection to the secondary winding where the electric field and flux density are highest). However, it has been found that both of the aforementioned techniques are rather cost-prohibitive to implement in static neutralization applications.
As a second shortcoming, conventional high-voltage, AC power supplies of the type described in detail above have been found to be limited in performance. In particular, the use of a transformer with a laminated core often results in oversaturation, which in turn limits the rise and minimizes the peak elevation of the output voltage under load.
As a third shortcoming, conventional high-voltage, AC power supplies of the type as described in detail above have been found to be rather rigid in design and difficult to assemble. Most notably, the inclusion of the relatively large, encapsulating, dielectric block renders the assembly process rather costly (due to the customized geometry of each block), time-consuming (to accommodate for the lengthy curing period of the encapsulating material) and structurally inflexible in nature. For instance, the output connectors are indirectly affixed the chassis through the fixedly mounted transformer core, since all components are encapsulated within a common dielectric block. To accommodate for the lack of flexibility in positioning the output connectors, the openings provided in the chassis to receive the output connectors are often slightly enlarged. This enlargement, or clearance, of each opening in the chassis results in small air gaps between the output port, or socket, for each output connector and the wall of the housing in which it is located. As referenced above, the presence of air gaps along the voltage supply path can result in partial electrical discharge, which in turn can degrade selected electrical components and/or dielectric materials (e.g., the encapsulating block or potting compound).